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Moher D, Schulz KF, Altman D, for the CONSORT Group. The CONSORT Statement: Revised Recommendations for Improving the Quality of Reports of Parallel-Group Randomized Trials. JAMA. 2001;285(15):1987–1991. doi:10.1001/jama.285.15.1987
Author Affiliations: University of Ottawa, Thomas C. Chalmers Centre for Systematic Reviews, Ottawa, Ontario (Mr Moher); Family Health International and Department of Obstetrics and Gynecology, School of Medicine, University of North Carolina at Chapel Hill (Dr Schulz); and ICRF Medical Statistics Group and Centre for Statistics in Medicine, Institute of Health Sciences, Oxford, England (Dr Altman).
To comprehend the results of a randomized controlled trial (RCT), readers
must understand its design, conduct, analysis, and interpretation. That goal
can be achieved only through complete transparency from authors. Despite several
decades of educational efforts, the reporting of RCTs needs improvement. Investigators
and editors developed the original CONSORT (Consolidated Standards of Reporting
Trials) statement to help authors improve reporting by using a checklist and
flow diagram. The revised CONSORT statement presented in this article incorporates
new evidence and addresses some criticisms of the original statement.
The checklist items pertain to the content of the Title, Abstract, Introduction,
Methods, Results, and Comment. The revised checklist includes 22 items selected
because empirical evidence indicates that not reporting the information is
associated with biased estimates of treatment effect or because the information
is essential to judge the reliability or relevance of the findings. We intended
the flow diagram to depict the passage of participants through an RCT. The
revised flow diagram depicts information from 4 stages of a trial (enrollment,
intervention allocation, follow-up, and analysis). The diagram explicitly
includes the number of participants, according to each intervention group,
included in the primary data analysis. Inclusion of these numbers allows the
reader to judge whether the authors have performed an intention-to-treat analysis.
In sum, the CONSORT statement is intended to improve the reporting of
an RCT, enabling readers to understand a trial's conduct and to assess the
validity of its results.
A report of a randomized controlled trial (RCT) should convey to the
reader, in a transparent manner, why the study was undertaken and how it was
conducted and analyzed. For example, a lack of adequately reported randomization
has been associated with bias in estimating the effectiveness of interventions.1,2 To assess the strengths and limitations
of an RCT, readers need and deserve to know the quality of its methods. Despite
several decades of educational efforts, RCTs still are not being reported
For example, a review of 122 recently published RCTs that evaluated the effectiveness
of selective serotonin reuptake inhibitors as first-line management strategy
for depression found that only 1 (0.8%) article described randomization adequately.5 Inadequate reporting makes the interpretation of RCT
results difficult if not impossible. Moreover, inadequate reporting borders
on unethical practice when biased results receive false credibility.
In the mid 1990s, 2 independent initiatives to improve the quality of
reports of RCTs led to the publication of the CONSORT (Consolidated Standards
of Reporting Trials) statement,7 which was
developed by an international group of clinical trialists, statisticians,
epidemiologists, and biomedical editors. CONSORT has been supported by a growing
number of medical and health care journals8-11
and editorial groups, including the International Committee of Medical Journal
Editors12 (ICMJE, also known as the Vancouver
Group), the Council of Science Editors (CSE), and the World Association of
Medical Editors (WAME). CONSORT is also published in Dutch, English, French,
German, Japanese, and Spanish. It can be accessed on the Internet, along with
other information about the CONSORT group.13
The CONSORT statement comprises a checklist and flow diagram for reporting
an RCT. For convenience, the checklist and diagram together are called simply CONSORT. They are primarily intended for use in writing,
reviewing, or evaluating reports of simple 2-group parallel RCTs.
Preliminary data indicate that the use of CONSORT does indeed help to
improve the quality of reports of RCTs.14,15
In an evaluation of 71 published RCTs in 3 journals in 1994, allocation concealment
was reported unclearly in 43 (61%) of the trials.14
Four years later, after these 3 journals required that authors reporting an
RCT use CONSORT, the proportion of articles in which allocation concealment
was reported unclearly had decreased to 30 of 77 (39%; mean difference, −22%;
[95% confidence interval, −38% to −6%]).14
The usefulness of CONSORT is enhanced by continuous monitoring of the
biomedical literature; this monitoring allows CONSORT to be modified depending
on the merits of maintaining or dropping current items and including new items.
For example, when Meinert16 observed that the
flow diagram did not provide important information about the number of participants
who entered each phase of an RCT (enrollment, treatment allocation, follow-up,
and data analysis), the diagram was able to be modified to accommodate the
information. The checklist is similarly flexible.
This iterative process makes the CONSORT statement a continually evolving
instrument. While participants in the CONSORT group and their degree of involvement
vary over time, members meet regularly to review the need to refine CONSORT.
At the 1999 meeting, participants decided to revise the original statement.
This report reflects changes determined by consensus of the CONSORT group,
partly in response to emerging evidence on the importance of various elements
Thirteen members of the CONSORT group met in May 1999 with the primary
objective of revising the original CONSORT checklist and flow diagram, as
needed. The group discussed the merits of including each item in the light
of current evidence. As in developing the original CONSORT statement, our
intention was to keep only those items deemed fundamental to reporting standards
for an RCT. Some items not considered essential may well be highly desirable
and still should be included in an RCT report even though they are not included
in CONSORT. Such items include approval of an institutional ethical review
board, sources of funding for the trial, and a trial registry number (eg,
the International Standard Randomized Controlled Trial Number [ISRCTN]) used
to register the RCT at its inception.17
Shortly after the meeting, a revised version of the checklist was circulated
to the group for additional comments and feedback. Revisions to the flow diagram
were similarly made. All these changes were discussed when CONSORT participants
met in May 2000, and the revised statement was finalized shortly afterward.
The revised CONSORT statement includes a 22-item checklist (Table 1) and a flow diagram (Figure 1). Its primary aim is to help authors improve the quality
of reports of simple 2-group parallel RCTs. However, the basic philosophy
underlying the development of the statement can be applied to any design.
In this regard, additional statements for other designs will be forthcoming
from the group.13 CONSORT can also be used
by peer reviewers and editors to identify reports with inadequate description
of trials and those with potentially biased results.1,2
During the 1999 meeting, the group also discussed the benefits of developing
an explanatory document to enhance the use and dissemination of CONSORT. The
document is patterned on reporting of statistical aspects of clinical research18 and was developed to help facilitate the recommendations
of the ICMJE's Uniform Requirements for Manuscripts Submitted
to Biomedical Journals. Three members of the CONSORT group, with assistance
from members on some checklist items, drafted an explanation and elaboration
document. That document19 was circulated to
the group for additions and revisions and was last revised after review at
the latest CONSORT group meeting.
(1) In the revised checklist, a new column for "paper section and topic"
integrates information from the "subheading" column that was contained in
the original statement.
(2) The "Was it reported?" column has been integrated into a "reported
on page #" column, as requested by some journals.
(3) Each item of the checklist is now numbered and the syntax and order
have been revised to improve the flow of information.
(4) "Title" and "Abstract" are now combined in the first item.
(5) While the content of the revised checklist is similar to the original,
some items that previously were combined are now separate. For example, authors
had been asked to describe "primary and secondary outcome(s) measure(s) and
the minimum important difference(s), and indicate how the target sample size
was projected." In the new version, issues pertaining to outcomes (item 6)
and sample size (item 7) are separate, enabling authors to be more explicit
about each. Moreover, some items request additional information. For example,
for outcomes (item 6) authors are asked to report any methods used to enhance
the quality of measurements, such as multiple observations.
(6) The item asking for the unit of randomization (eg, cluster) has
been dropped because specific checklists have been developed for reporting
cluster RCTs20 and other design types13 since publication of the original checklist.
(7) Whenever possible, new evidence is incorporated into the revised
checklist. For example, authors are asked to be explicit about whether the
analysis reported is by intention-to-treat (item 16). This request is based
in part on the observations21 that authors
do not adequately describe and apply intention-to-treat analysis and reports
that not providing this information are less likely to provide other relevant
information, such as loss to follow-up.22
(8) The revised flow diagram depicts information from 4 stages of a
trial (enrollment, intervention allocation, follow-up, and analysis). The
revised diagram explicitly includes the number of participants, according
to each intervention group, included in the primary data analysis. Inclusion
of these numbers lets the reader know whether the authors have performed an
Because some of the information may not always be known and to accommodate
other information, the structure of the flow diagram may need to be modified
for a particular trial. Inclusion of the participant flow diagram in the report
is strongly recommended but may be unnecessary for simple trials, such as
those without any participant withdrawals or dropouts.
Specifically developed to guide authors about how to improve the quality
of reporting of simple 2-group parallel RCTs, CONSORT encourages transparency
in reporting the methods and results so that reports of RCTs can be interpreted
both readily and accurately. However, CONSORT does not address other facets
of reporting that also require attention, such as scientific content and readability
of RCT reports. Some authors, in their enthusiasm to use CONSORT, have modified
the checklist.24 We recommend against such
modifications because they may be based on a different process than the one
used by the CONSORT group.
The use of CONSORT seems to reduce (if not eliminate) inadequate reporting
of RCTs.14,15 Potentially, the
use of CONSORT should positively influence the manner in which RCTs are conducted.
Granting agencies have noted this potential relationship and, in at least
1 case,25 have encouraged grantees to consider
in their application how they have dealt with the CONSORT items.
The evidence-based approach used to develop CONSORT also has been used
to develop standards for reporting meta-analyses of randomized trials,26 meta-analyses of observational studies,27
and diagnostic studies (Jeroen Lijmer, MD, written communication, October
2000). Health economists also have started to develop reporting standards28 to help improve the quality of their reports.29 The intent of all these initiatives is to improve
the quality of reporting of biomedical research30
and by doing so to bring about more effective health care.
The revised CONSORT statement will replace the original one in the journals
and groups that already support it. Journals that do not yet support CONSORT
may do so by registering on the CONSORT Web site.13
To convey to authors the importance of improved quality in the reporting of
RCTs, we encourage supporting journals to reference the revised CONSORT statement
and the CONSORT Internet address13 in their
"Instructions to Authors." Because the journals publishing the revised CONSORT
statement have waived copyright protection, CONSORT is now widely accessible
to the biomedical community. The CONSORT checklist and flow diagram can also
be accessed at the CONSORT Web site.13
A lack of clarification of the meaning and rationale for each checklist
item in the original CONSORT statement has been remedied with the development
of the CONSORT explanation and elaboration document,19
which also can be found on the CONSORT Web site.13
This document reports the evidence on which the checklist items are based,
including the references, which had annotated the checklist items in the previous
version. We encourage journals to also include reference to this document
in their Instructions to Authors.
Emphasizing the evolving nature of CONSORT, the CONSORT group invites
readers to comment on the updated checklist and flow diagram through the CONSORT
Web site.13 Comments and suggestions will be
collated and considered at the next meeting of the group in 2001.